You'll Only See this Magnum Ice-Cream Ad When it's Hot Out

Published on December 31, 1969.

Unilever UK is counting on a warm English summer to justify its 2 million-pound campaign ($3.04 million) for the limited edition Magnum Kisses. The company's leading ice cream brand has developed a new set of dessert flavors, like Tarte aux Pommes and Meringue et Fruits Rouges, inspired by classic French patisseries. Some of that investment can be seen on the roofs of 25 London black cabs -- but only if it's above 19 degrees Celsius (66 degrees Fahrenheit) on overcast days and 16 degrees Celsius (61 degrees Fahrenheit) on sunny ones.

Magnum has partnered with BrightMove Media to create TaxiCast -- heat-activated ads in the form of high-visibility LED screens that only light up if the heat, humidity and brightness are just right. The system has a remote deployment system that uses private and secure links via 3G networks to update the geo-located digital platforms' content in real time. The appeal of this medium for Magnum is the key commuter group it can reach between 7 a.m. and 10 a.m., including those in less-accessible areas like Square Mile and Regent Street. The campaign, which launched earlier this month was initially given a three month trial on a set number of cabs, due to the highly regulated nature of the city's transport sector.